krystle campbell, 29, lingzi lu, 23 and martin richard, just 8. and police officer sean collier, 26, murdered allegedly by the suspects. at m.i.t. today a tribute where collier died on campus. >> i see a young man with incredible potential. i think the sky was the limit with him, and i think that in the future we would have heard a lot from him. m.i.t. is a real special place, and it is the real deal, and they deserve the reputation they have is deserved beyond deserved. but this is a whole other side that i'm starting to see. >> reporter: more than 50 people wounded in the blast remain hospitalized, including a 7-year-old girl in critical condition, and transit officer richard donahue, ironically a close friend of officer collier, gravely wounded during the chase for the two suspects. >> he works for the transit, and i'll always tell him you're never going to see any action because you're on the subway. but, you know, there he is jumping into the midst of a gunfight in watertown and making transit very proud. >> reporter: at the university of mas